check multiple ng-model values to change the caption of the button - angularjs

Question

i need to change the caption of the button based on the value of multiple model values. i have a button. when the model values are null, it should display "Load" and if not then "refresh". If i check with one model value it works fine. How do i check entire model values.
<button id="load" type="submit" class="btn btn-success" style="float:right" > {{processState.widgetInstance.configuration.application ? 'Refresh':'Load'}}</button>
<ul>
<li>Application:
<select name="application" required ng-model="processState.widgetInstance.configuration.application" ng-options="app.APP_ID as app.APP_NAME for app in applications">
</select>
</li>
<li>Namespace:
<select name="namespace" required ng-model="processState.widgetInstance.configuration.namespace" ng-options="namespace.NAMESPACE_ID as namespace.NAMESPACE for namespace in namespace">
</select>
</li>
</ul>
In this case, if the select combo has values, it should display refresh else load. the values for the scope variables are populated from a service in this case.
Plunker
Working Copy

Answer 1

Just use parenthesis and && operator
angular.module("app",[]).controller("ctrl", function($scope){
});
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.23/angular.min.js"></script>
<div ng-app="app" ng-controller="ctrl">
<button id="load" type="submit" class="btn btn-success" style="float:right" > {{(application && namespace) ? 'Refresh':'Load'}}</button>
<ul>
<li>Application:
<input ng-model="application" type="text"/>
</li>
<li>Namespace:
<input ng-model="namespace" type="text"/>
</li>
</ul>
</div>

Answer 2

you can use angular form validation http://plnkr.co/edit/UZIqF2qG4UyNdbH4NSHu?p=preview
<button id="load" type="submit" class="btn btn-success" style="float:right"> {{ myform.$valid ? 'Refresh': 'Load' }}</button>
<form name='myform'>
<ul>
<li>Application:
<select name="application" required ng-model="processState.widgetInstance.configuration.application" ng-options="app.APP_ID as app.APP_NAME for app in applications">
</select>
</li>
<li>Namespace:
<select name="namespace" required ng-model="processState.widgetInstance.configuration.namespace" ng-options="namespace.NAMESPACE_ID as namespace.NAMESPACE for namespace in namespace">
</select>
</li>
<li>Products:
<select name="product" required ng-model="processState.widgetInstance.configuration.product" ng-options="product.PRODUCT_ID as product.PRODUCT_NAME for product in product">
</select>
</li>
</ul>
</form>